Question

我做了一个小应用程序，可以在多台显示器上快速更改屏幕分辨率。我想将产品名称显示为显示器的标题，使用此代码查找非常简单：

NSDictionary *deviceInfo = (__bridge NSDictionary *)IODisplayCreateInfoDictionary(CGDisplayIOServicePort(dispID), kIODisplayOnlyPreferredName);

NSDictionary *localizedNames = [deviceInfo objectForKey:[NSString stringWithUTF8String:kDisplayProductName]];

if([localizedNames count] > 0) {
    _title = [localizedNames objectForKey:[[localizedNames allKeys] objectAtIndex:0]];
} else {
    _title = @"Unknown display";
}

但是在OS X＆gt; = 10.9中不推荐CGDisplayIOServicePort，Apple的文档说没有替代品。如何在不使用此方法的情况下查找服务端口或产品名称？

我试图遍历IO注册表并尝试使用IOServiceGetMatchingServices方法来查找显示服务，但我对IO注册表不太熟悉，所以我找不到解决方案。

感谢您的帮助！

Answer 1

看起来@Eun的帖子错过了关闭此讨论的一条信息。通过一点点搜索，我发现IOServicePortFromCGDisplayID不是Apple提供的API。相反，它是一个在这里找到的开源代码： https://github.com/glfw/glfw/blob/e0a6772e5e4c672179fc69a90bcda3369792ed1f/src/cocoa_monitor.m

我从中复制了IOServicePortFromCGDisplayID和'getDisplayName'。我需要进行两次调整才能使其在OS X 10.10上运行。

删除代码以处理IOServicePortFromCGDisplayID中的序列号。（CFDictionaryGetValue for kDisplaySerialNumber为我返回NULL。）
删除特定项目 getDisplayName中的错误处理代码。

如果您需要更多信息

问题跟踪器：github.com/glfw/glfw/issues/165
提交解决方案： github.com/glfw/glfw/commit/e0a6772e5e4c672179fc69a90bcda3369792ed1f

我要感谢Matthew Henry在那里提交了代码。

Answer 2

以下是我对这个问题的看法。我还从GLFW 3.1的代码开始，文件cocoa_monitor.m 但我必须以不同的方式修改它，而不是Hiroshi说的，所以这里是：

// Get the name of the specified display
- (NSString*) screenNameForDisplay: (NSNumber*) screen_id
{
    CGDirectDisplayID displayID = [screen_id unsignedIntValue];

    io_service_t serv = [self IOServicePortFromCGDisplayID: displayID];
    if (serv == 0)
        return @"unknown";

    CFDictionaryRef info = IODisplayCreateInfoDictionary(serv, kIODisplayOnlyPreferredName);
    IOObjectRelease(serv);

    CFStringRef display_name;
    CFDictionaryRef names = CFDictionaryGetValue(info, CFSTR(kDisplayProductName));

    if ( !names ||
         !CFDictionaryGetValueIfPresent(names, CFSTR("en_US"), (const void**) & display_name)  )
    {
        // This may happen if a desktop Mac is running headless
        CFRelease( info );
        return @"unknown";
    }

    NSString * displayname = [NSString stringWithString: (__bridge NSString *) display_name];
    CFRelease(info);
    return displayname;
}


// Returns the io_service_t (an int) corresponding to a CG display ID, or 0 on failure.
// The io_service_t should be released with IOObjectRelease when not needed.

- (io_service_t) IOServicePortFromCGDisplayID: (CGDirectDisplayID) displayID
{
    io_iterator_t iter;
    io_service_t serv, servicePort = 0;

    CFMutableDictionaryRef matching = IOServiceMatching("IODisplayConnect");

    // releases matching for us
    kern_return_t err = IOServiceGetMatchingServices( kIOMasterPortDefault, matching, & iter );
    if ( err )
        return 0;

    while ( (serv = IOIteratorNext(iter)) != 0 )
    {
        CFDictionaryRef displayInfo;
        CFNumberRef vendorIDRef;
        CFNumberRef productIDRef;
        CFNumberRef serialNumberRef;

        displayInfo = IODisplayCreateInfoDictionary( serv, kIODisplayOnlyPreferredName );

        Boolean success;
        success =  CFDictionaryGetValueIfPresent( displayInfo, CFSTR(kDisplayVendorID),  (const void**) & vendorIDRef );
        success &= CFDictionaryGetValueIfPresent( displayInfo, CFSTR(kDisplayProductID), (const void**) & productIDRef );

        if ( !success )
        {
            CFRelease(displayInfo);
            continue;
        }

        SInt32 vendorID;
        CFNumberGetValue( vendorIDRef, kCFNumberSInt32Type, &vendorID );
        SInt32 productID;
        CFNumberGetValue( productIDRef, kCFNumberSInt32Type, &productID );

        // If a serial number is found, use it.
        // Otherwise serial number will be nil (= 0) which will match with the output of 'CGDisplaySerialNumber'
        SInt32 serialNumber = 0;
        if ( CFDictionaryGetValueIfPresent(displayInfo, CFSTR(kDisplaySerialNumber), (const void**) & serialNumberRef) )
        {
            CFNumberGetValue( serialNumberRef, kCFNumberSInt32Type, &serialNumber );
        }

        // If the vendor and product id along with the serial don't match
        // then we are not looking at the correct monitor.
        // NOTE: The serial number is important in cases where two monitors
        //       are the exact same.
        if( CGDisplayVendorNumber(displayID) != vendorID ||
            CGDisplayModelNumber(displayID)  != productID ||
            CGDisplaySerialNumber(displayID) != serialNumber )
        {
            CFRelease(displayInfo);
            continue;
        }

        servicePort = serv;
        CFRelease(displayInfo);
        break;
    }

    IOObjectRelease(iter);
    return servicePort;
}

在我使用macOS 10.11（El Capitan）编写的屏幕保护程序中，这对我来说很好。我使用MacBookPro的内置显示器和通过Thunderbolt连接的Apple Display进行了测试。

Answer 3

NSString* screenNameForDisplay(CGDirectDisplayID displayID)
{
    NSString *screenName = nil;
    io_service_t service = IOServicePortFromCGDisplayID(displayID);
    if (service)
    {
        NSDictionary *deviceInfo = (NSDictionary *)IODisplayCreateInfoDictionary(service, kIODisplayOnlyPreferredName);
        NSDictionary *localizedNames = [deviceInfo objectForKey:[NSString stringWithUTF8String:kDisplayProductName]];

        if ([localizedNames count] > 0) {
            screenName = [[localizedNames objectForKey:[[localizedNames allKeys] objectAtIndex:0]] retain];
        }

        [deviceInfo release];
    }
    return [screenName autorelease];
}

在OS X＆gt; = 10.9中不推荐使用CGDisplayIOServicePort，如何替换？

3 个答案: